Roles Of Pentatricopeptide Repeat Proteins Research Articles

A Genome-Wide Analysis of the Pentatricopeptide Repeat Protein Gene Family in Two Kiwifruit Species with an Emphasis on the Role of RNA Editing in Pathogen Stress.

Kiwifruit is a perennial fruit tree with high nutritional and economic value; however, various pathogen stresses have resulted in reductions in its yield and quality. Pentatricopeptide repeat proteins (PPRs), characterized by tandem repetitions of 35 amino acid motifs, play roles in RNA editing, mRNA stability, and splicing. They may also regulate plant development and growth. Nevertheless, the roles of PPRs in plant development and disease resistance remain unclear. In this study, we focused on the roles of PPRs in the fruit development and pathogen stress of kiwifruit and conducted a series of analyses of the PPR gene family in two representative kiwifruit species (Actinidia chinensis (Ach) and Actinidia eriantha (Ace)) with markedly different degrees of disease resistance. A total of 497 and 499 PPRs were identified in Ach and Ace, respectively. All the kiwifruit PPRs could be phylogenetically divided into four subfamilies. There were about 40.68% PPRs predicted to be localized to mitochondria or chloroplasts. A synteny analysis showed that the expansion of the kiwifruit PPRs mainly originated from segmental duplication. Based on RNA-seq data from the fruit over 12 periods of development and maturity, a weighted correlation network analysis suggested that two PPRs, Actinidia20495.t1 and Actinidia15159.t1, may be involved in fruit development and maturation. In addition, we observed different responses with respect to the expression of PPRs and RNA editing between resistant and susceptible kiwifruits following infection with pathogenic bacteria, indicating the regulatory role of PPRs in the stress response via the modulation of RNA editing. The differentially expressed upstream transcription factors of the PPRs were further identified; they may regulate resistance adaption by modulating the expression of the PPRs. Collectively, these results suggest that PPRs play roles in the development and disease resistance of kiwifruit and provide candidate genes for further clarifying the resistance mechanisms in kiwifruits.

The role of PPR proteins in posttranscriptional regulation of organelle components in plants.

Pentatricopeptide repeat (PPR) proteins constitute one of the largest protein families in land plants. They are sequence-specific RNA-binding proteins and play key roles in posttranscriptional processes within organelles. Their combined actions have profound effects on chloroplast photosynthetic electron transport chain and mitochondrial respiratory chain, affecting photosynthesis and respiration respectively, and ultimately on yield, fertility, and grain quality. Over the past decade, much has been learned about the molecular functions of these proteins on plant growth and development. However, due to the large size of this protein family, the functions of most members remain largely unknown. Here, we summarize the molecular mechanisms of PPR proteins functions on organelle genes, and effects on development of organelles and plants. Problems that need to be resolved are also identified. This article will provide a theoretical basis for understanding the functions of PPR protein family and genetic improvements of grain yield and quality.